A Conventional yarn feeder for knitting machines such as the one shown in FIGS. 1 and 2 usually includes a frame A, a feeding reel B, a brake C, a pulley D, a holder E, a transmission spindle F and a yarn guide G. The feeding reel B is located below the frame A and held by the holder E and driven by the transmission spindle F which passes through the frame A to engage with the pulley D located above the frame A. The rotating pulley D drives the yarn reel B to rotate for pulling yarn I from a yarn pool H. The yarn I leaves the yarns pool H, passes through a guide bracket J, a filter K, a press disk L, below an upper brake lever M, a first porcelain eye N, winds a number of times around the yarn reel B, then passes through above a porcelain bar of the yarn guide G, below a lower brake lever O, a second porcelain eye Q and reaches a knitting needle for knitting process. The yarn reel B provides a stable tension yarn for producing high quality fabric. The yarn reel B includes a driving wheel S engaged with a driven wheel T which has a spindle opening U engaged with a bearing R which in turn engages with the holder E and mounted below the frame A. The yarn reel B thus is able to turn freely about the bearing R.
The driven wheel T has a plurality of equally spaced rods V extending downward. Below the driven wheel and between a pair of adjacent rods V, a cavity bore W is formed. The driving wheel S has a center spindle bore X enageable with one end of the spindle F and a plurality of elongated bars Y engaged with the cavity bores W when assembled with the driven wheel T. The yarn reel B has a taper angle from the top of the driven wheel T to the bottom of the driving wheel S so that yarn I wound around the yarn reel B may slip downward during the knitting process to make yarn feeding smooth and steady. As the driving wheel T and the rods V are usually made by injection molding plastics, the precision of the rods V is often less than desired. When in use, one end of the rod V engages with the driving wheel S which may increase dimensional distortion of the elongated bars Y. The dimensional accuracy of the yarn reel B after assembly thus may be further downgraded.
The holder E is made of metal and has an inclined top surface mounted on the frame A through a washer (not shown). It takes a lot of machining work to attain the precision required. The machining of the spindle F is equally demanding and time consuming. All this increases production time and cost.
Furthermore the press disk L uses a spring force to give yarn a tension. It does not finction well for thin or smooth yarns and may result in yarn dropping from the yarn reel B which affects the knitting machine operation. All of aforesaid problems and disadvantages are still begging for improvement.